I LOVE finding out about different ways to appreciate the Sun and light in general. Use this forum to post your info or questions about various outside the mainstream ways to appreciate our life giving star!

Here is an animation showing the solar disk in a spectral sweep through the H alpha line. The change in wavelength from one frame to the next is 0.054 Angstroms and the wavelength offset (in milliAngstroms) from line centre is displayed in the upper left portion of the frames.

The spectral bandpass of the spectroheliograph in its present configuration is ~200 milliAngstroms (fwhm).

Cheers, Peter.

2018-08-08-083838-Ha spectral sweep.gif (6.58 MiB) Viewed 1391 times

Last edited by p_zetner on Wed Aug 15, 2018 6:36 pm, edited 1 time in total.

Here is a montage of the 25 frames of the animation showing the actual intensity variation from frame to frame (a few of the frame numbers are displayed). I eliminated this intensity variation in the animation (using histogram normalization in ImageJ) because it made the central frames of the animation too dim to view. As in the animation, the wavelength offset between adjacent disk images is 0.054 Angstroms.

If I take the mean disk intensity in each frame and plot it (blue crosses) on a measured spectrum it matches the H alpha line profile pretty closely, as expected but always a pleasant surprise when things work out!

The image to the left is an average over 23 frames of a (spectral) calibration video taken with the spectroheliograph. The yellow box shows the region of the spectrum (approximately) that is plotted on the right side of the figure. The spectrum is calibrated in wavelength using line positions from the BASS2000 solar spectrum.

Cheers, Peter.

Last edited by p_zetner on Thu Aug 16, 2018 4:43 pm, edited 1 time in total.

Marvellous and very informative. Thanks for sharing !
Could you slow do a little bit the movie ?
It seems to me that the "spicules bushes" are best visible at +/- 0.4A.
Could you make another monatge with larger resolution ? Let's say with the solar disk twice the size of this first montage ?

Excellent work, as always, Peter. Very helpful to see the sweep like this.
It's interesting to see the various subtle Doppler effects within the filaments as the sweep progresses through the wavelengths.

I find the behaviour of the filaments, as you sweep through the line, interesting as well, especially the one lying halfway between disk centre and the E limb. A part of it seems to persist over a large portion of the sweep, suggesting a high temperature? I'm just finishing some analysis of its spectrum at the moment and will post the results.